A conventional inertial force sensor will be described with reference to FIG. 18. FIG. 18 is a block diagram of conventional inertial force sensor 1. Inertial force sensor 1 has vibrator 2, self-excited vibration circuit 3, detection circuit 4, power source control device 5, and trigger signal input unit 6. Self-excited vibration circuit 3 causes a drive vibration of vibrator 2. Detection circuit 4 is connected to vibrator 2 and outputs an inertial force value. Power source control device 5 controls power supplied to self-excited vibration circuit 3 and detection circuit 4. Trigger signal input unit 6 is connected to power source control device 5.
When detection circuit 4 does not detect the amount of inertia, power source control device 5 reduces power to be supplied to a part of self-excited vibration circuit 3 and detection circuit 4. Also, power source control device 5 restores the power supplied to the part being supplied with the reduced power to a rated power based on a trigger input from trigger signal input unit 6.